EVA insole manufacturing process

ABSTRACT

An EVA insole manufacturing process includes a step of mixing an EVA resin with a foaming agent for producing a molding through squeezing and cutting procedures, and a step of heating the molding thus obtained in a mold so that it forms into a predetermined shape. Two or more moldings which respectively contain a different concentration of foaming agent or a different pigment color may be molded together so as to produce an insole which has different hardness and color at different parts thereof.

BACKGROUND OF THE INVENTION

The present invention relates to an EVA insole manufacturing process formaking EVA (ethylene vinyl acetate copolymer resin) insoles.

U.S. Pat. No. 5,141,578 issued to the inventor of the present invention,discloses an EVA insole manufacturing process which includes a step ofmixing an EVA resin with a foaming agent for producing a molding throughan injection molding process, and a step of heating the molding thusobtained in a mold so that it foams into a predetermined shape. Two ormore moldings which respectively contain a different concentration offoaming agent or a different pigment color may be put together in acommon mold and subjected to integral foaming and form setting process,so as to produce an insole which has different hardness and color atdifferent parts thereof. This EVA insole manufacturing processeliminates the disadvantages of a conventional EVA insole manufacturingprocess, which includes a first step to mix an EVA resin with a foamingagent and then squeezing the mixture into strips, a second step to placethe EVA material strips in a hot press and letting it be subjected to afoaming process, a third step to place the foamed EVA strip in a watercooling trough for cooling and then cutting or trimming the foamed EVAstrips, a fourth step to grind the EVA strips and then put them in ahydraulic machine for form setting. The EVA insole manufacturing processaccording to U.S. Pat. No. 5,141,578 consumes less human power, canfully utilize EVA material and greatly increase production capacity.However, it is still time consuming in forming a first molding and asecond molding and form setting the integral molding obtained fromputting the second molding within an opening on the first molding andheat foaming both the first and second moldings together in a mold.Further, this process needs much equipment including at least a crusher,an injection molding machine, a heat press, a hydraulic machine. Becauseof the use of the aforesaid necessary equipment, the hardware equipmentcost and regular hardware equipment maintenance cost become inevitablyhigh.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the aforesaidcircumstances. According to the present invention, an EVA insole isdirectly molded from a molding which is obtained from cutting an EVAresin and foaming agent mixture. This method eliminates the use of aninjection molding machine and a crusher. The residual EVA materialresulted from the cutting can be collected and then squeezed into flatblocks for use again, and therefore manufacturing loss is minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a molding which is made of an EVA resin throughsqueezing and cutting procedures, and an insole which is made of amolding through foaming and form setting process;

FIG. 2 illustrates two different moldings according to the presentinvention; and

FIG. 3 illustrates an integral insole made of two different moldingsaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, EVA resin is proportionally mixed with a foamingagent and then squeezed into a flat block. The flat block thus obtainedis then properly cut and trimmed to form into moldings 10 according to apredetermined pattern. Each molding 10 is then placed in a mold andheated so that it foams. After the foaming process in the mold by use ofa heat press, the foamed molding is removed from the mold and then,placed in a hydraulic machine for form setting. After form setting, afinished insole 20 is made.

An insole may be so made that its different parts have differenthardness. As shown in FIG. 2, two separate moldings 30,40 arerespectively made of different EVA materials through the aforesaidsqueezing and cutting processes, wherein the EVA material for making afirst molding 30 contains a foaming agent in a concentration differentfrom the EVA material used for making a second molding 40. Further, theEVA material for making a first molding 30 may contain a pigment colorwhich is different from the EVA material for making a second molding 40.The first molding 30 is relatively bigger, having a trough definedtherein for receiving the second molding 40, so that the second molding40 can be placed inside the first molding 30 and then both the first andsecond moldings are put into a mold of a hot press for foaming into anintegral molding, which is then placed in a hydraulic machine and formset into a finished insole. The insole thus obtained has a unitary innerpart 60 and outer part 50 in different hardness and/or color, as shownin FIG. 3.

As described above, an EVA insole in accordance with the presentinvention is made of EVA moldings through foaming and shape moldingprocess, which EVA moldings are made of EVA material chips containingdifferent concentrations of an EVA resin and a foaming agent and whichare formed through squeezing and cutting procedures. Different parts ofan insole can be made in different hardness and different color, asdesired.

I claim:
 1. An EVA insole manufacturing process comprising the stepsof:(i) forming a first molding portion and a second molding portionrespectively by the steps of:(a) mixing an ethylene vinyl acetate resinwith a foaming agent according to a predetermined proportion, andsqueezing the resulting mixture into a flat block; and, (b) cutting therespective flat block into the first molding portion and the secondmolding portion, so that the first molding portion has an opening forreceiving the second molding portion; (ii) placing the second moldingportion within the opening of the first molding portion; (iii) heatfoaming both the first and second molding portions together in a mold toform an integrally molded article; and (iv) form setting the integrallymolded article into an insole.
 2. An EVA insole manufacturing processcomprising the steps of:i) forming a first molding portion by the stepsof:(a) mixing an ethylene vinyl acetate resin with a foaming agentaccording to a first concentration and squeezing the resulting mixtureinto a first flat block; and, b) cutting the first flat block into thefirst molding portion so that the first molding portion has an openingfor receiving a second molding portion; ii) forming a second moldingportion by the steps of:a) mixing an ethylene vinyl acetate resin with afoaming agent according to a second concentration different from thefirst concentration and squeezing the resulting mixture into a secondflat block; and, b) cutting the second flat block into the secondmolding portion; iii) placing the second molding portion within theopening in the first molding portion; iv) heat foaming both the firstand second molding portions together in a mold to form an integrallymolded article; and, v) form setting the integrally molded article intoan insole.
 3. The method of claim 2 further comprising the step ofadding a pigment color to one of the first and second molding portionssuch that the first and second molding portions have different colors.